Metabolic effects of fasting on human and mouse blood in vivo

Abstract

Starvation is a strong physiological stimulus of macroautophagy/autophagy. In this study, we addressed the question as to whether it would be possible to measure autophagy in blood cells after nutrient deprivation. Fasting of mice for 48 h (which causes »20% weight loss) or starvation of human volunteers for up to 4 d (which causes <2% weight loss) provokes major changes in the plasma metabolome, yet induces only relatively minor alterations in the intracellular metabolome of circulating leukocytes. White blood cells from mice and human volunteers responded to fasting with a marked reduction in protein lysine acetylation, affecting both nuclear and cytoplasmic compartments. In circulating leukocytes from mice that underwent 48-h fasting, an increase in LC3B lipidation (as assessed by immunoblotting and immunofluorescence) only became detectable if the protease inhibitor leupeptin was injected 2 h before drawing blood. Consistently, measurement of an enhanced autophagic flux was only possible if white blood cells from starved human volunteers were cultured in the presence or absence of leupeptin. Whereas all murine leukocyte subpopulations significantly increased the number of LC3B C puncta per cell in response to nutrient deprivation, only neutrophils from starved volunteers showed signs of activated autophagy (as determined by a combination of multi-color immunofluorescence, cytofluorometry and image analysis). Altogether, these results suggest that white blood cells are suitable for monitoring autophagic flux. In addition, we propose that the evaluation of protein acetylation in circulating leukocytes can be adopted as a biochemical marker of organismal energetic status.

Measuring biological aging in humans: A quest

“…They could detect enhanced autophagic flux in human neutrophils cultured in the presence or absence of leupeptin (Pietrocola et al, 2017). Although these methods are promising, further development and validation in human cells is needed before these assays can be used in clinical studies.…”

“…Also, using prolonged starvation in human volunteers, Pietrocola et al developed a method to assess autophagy in circulating leukocytes. They could detect enhanced autophagic flux in human neutrophils cultured in the presence or absence of leupeptin (Pietrocola et al, ). Although these methods are promising, further development and validation in human cells is needed before these assays can be used in clinical studies.…”

CD44 regulates epigenetic plasticity by mediating iron endocytosis

“…Metabolomics experiments were performed and analyzed as previously described (Pietrocola et al, 2018;Pietrocola et al, 2017). Briefly, for sample preparation, cells were grown in 6-well plates and treated as indicated.…”

Autophagy and Its Implications Against Early Full Nutrition Support in Critical Illness

“…In addition, in vivo monitoring of autophagy is problematic, as this requires extensive laboratory testing and repetitive biopsies . Although autophagy monitoring on white blood cells could be a readout for the autophagy status in other organs, this has not been validated in critically ill patients . Moreover, the activation status of autophagy may slightly differ between organs …”